Spatial variation in selected vegetable crops in Tennessee

Modern technology, environmental concerns, and economics are a few of the reasons that today's producers are forced to develop better ways to produce crops than in previous years. The technologies and practices of site-specific farming or prescription farming is rapidly spreading across the farming industry. The ability to spatially control the application rates within a field is revolutionizing the modem farm.

To evaluate the feasibility of this new technology, the degree of spatial variation present in the field should be known. The history of the field and the crops must be documented as well as the requirements for the crop to be grown. In recent years there has been considerable research in the area of site-specific farming relating to grain and cereal crops. However, there has been little research, on site-specific farming in vegetable production.

During the 1993 growing season The University of Tennessee Departments of Agricultural Engineering, Plant and Soil Science conducted an experiment in conjunction with PictSweet Inc., a commercial vegetable producer, to document the magnitude of spatial variation and the effect of the variation on yield of two vegetable crops. Two fields in West Tennessee that were in production by the producer were selected. The first field was in vegetable production for the first time by the producer and the crop grown was Italian green beans. The second field had been in vegetable production for several years. The crop under investigation in this field was butter beans. Plots were established in both fields which measured ten feet in length along a single bed Each field was monitored for plant response, soil moisture, and soil fertility.

Soil fertility variables considered from each plot include aluminum, calcium, copper, iron, potassium, magnesium, manganese, sodium, phosphorus, zinc, and pH. Measurements of these soil variables were collected twice during the growing season of the crop and at two depths, 6-12 inches. Soil moisture samples were taken several times during the growing season using a neutron probe. These variables were then analyzed graphically and statistically to study the variation of each across the fields and to determine their effects on the crops.

Spatial variation existed across both fields not only in yields but also in the other variables measured and collected. Results suggested that there was not any single limiting variable in the study. However, it was apparent that there were interactions between variables that had an effect on yield. It was also noted that interactions not measured in this study played a role in spatial variation in the crops. Many of these variables were management controlled.